1. Field of the Invention
The present invention relates to an image sensing apparatus for sensing a still image and/or moving image.
2. Description of the Related Art
Conventionally, image sensing apparatuses such as electronic cameras and the like, which record/play back still images and moving images sensed by a solid-state image sensing element such as a CCD or the like using memory cards having solid-state memory elements as recording media, have already been commercially available.
In an electronic camera using such solid-state image sensing element such as a CCD or the like, a dark noise correction process can be done by computations using dark image data which is read out after charge accumulation in the same manner as in actual image sensing while the image sensing element is not exposed, and actually sensed image data which is read out after charge accumulation while the image sensing element is exposed.
With this process, sensed image data can be corrected for image quality deterioration such as pixel omission or the like caused by dark current noise produced by the image sensing element and small scratches unique to the image sensing element, thus obtaining a high-quality sensed image.
Especially, since dark current noise increases with increasing charge accumulation time and temperature rise of the image sensing element, if exposure for a long period of time (seconds) or at high temperature is done, a great image quality improvement effect can be obtained, and the dark noise correction process is a function useful for the electronic camera users.
In this manner, since dark current noise increases with increasing charge accumulation time and temperature rise of the image sensing element, dark image data is re-captured using the charge accumulation time of the image sensing element in units of image sensing processes.
For this reason, when actual image sensing is done after dark image data is captured, the shutter release time lag becomes longer by the dark image sensing time, thus missing a shutter chance.
On the other hand, when dark image data is captured after actual image sensing, the image sensing interval between the first and second frames is prolonged by the dark image sensing time in the continuous shot mode. As a result, constant image sensing frame intervals cannot be set.
Furthermore, in either case, since the dark image capture process is repeated upon each image sensing, the consumption power increases accordingly.